The Afterlife is what happens to a person after death. In comics there are many interpretations of an afterlife in real life and in comics. There are also many heroes who work and/or live in the Afterlife such as DC Comics' Deadman, Spectre and the Ragman.
Ragman literally wears the afterlife as his costume. Each rag in his costume is an evil soul that lives in purgatory and gives the wearer of his costume power.
Spectre is literally risen from the dead and is allowed to deal vengeance for the christian God.
Dark Horse Comics
Ghost believed her self to be dead and that opened up many questions about the the afterlife. For every answer she got about the afterlife two more questions would pop up. She eventually found out she wasn't even dead and that she had ghostlike powers.